The charger is a slow starter, it need nearly 20 seconds before it has reached full current.

I wanted a close look at the spikes, it is a 10ms pause to measure voltage and a very short spike when starting charging again.

With more batteries in the charger the current will be reduced.

With adjacent batteries (1-2, 3-4, 5-6) the charger switches between the two slots.

The charger passed the 2830 volt and 4242 volt test, this means it is it is fairly safe.

Conclusion

The charger works fine, but due to the 2A charge current it is only for some 18650 and for larger batteries. I would have preferred some slots dedicated for lower charge current. The "quick charger" can be discussed, speeds depends on number of batteries and slots used.

As long as the charger is used for high current 18650 and larger batteries it is a fairly good charger.